Aircraft in flight are commonly refueled from a refueling aircraft. The refueling aircraft is typically provided with a boom mechanism or a flexible hose which trails behind the aircraft and physically makes a connection to the aircraft to be refueled. Common refueling aircraft have a plurality of wing fuel tanks and a central wing tank. Auxiliary fuel tanks can also be provided within or proximate to a fuselage of the aircraft. Fuel is commonly transferred to the boom or hose via a single wall header which is isolable by one or more shut-off valves. Common refueling systems include pumps to pressurize the fuel for transfer from one or more of the tanks, and valves which are controlled between an open and closed condition by simple on-off switches normally positioned on a refueling system panel and manually selected by a trained refueling operator.
Common refueling systems require the refueling operator within the refueling aircraft to visually monitor flow and pressure indicators and communicate to the receiving aircraft whose operator/pilot can monitor fuel tank levels. The refueling operator is responsible to manually initiate and shut down the flow of fuel. Inadvertent disconnect of the refueling boom or hose can therefore occur before the receiving aircraft receives a full fuel load if an excess number of fuel transfer pumps are operated or if a pressure spike occurs. Some systems provide automatic disconnect of the refueling boom or hose upon reaching a predetermined fuel over-pressure condition. Because of the use of manual monitoring and manual shut-off of fuel flow, operation of these refueling systems also can result in overfilling of the receiving aircraft fuel tanks and subsequent relief valve discharge of fuel.